Shaft seals, also known as lip seals, are versatile mechanical components that maintain dynamic seals around rotating components, such as rotating shafts. Common examples of radial and piston shaft seals include, without limitation, strut seals, hydraulic pump seals, axle seals, power steering seals, and valve stem seals. A different seal design for similar applications is called a rotating face seal. The basic working principle of a modern shaft seal is compressing a wear-resistant material, such as an elastomer, against the rotating component using a press-fit, ordinarily with a garter or cantilever spring to provide additional compression.
As the shaft rotates inside the shaft seal, seal material is slowly abraded from the shaft seal, thereby reducing its effectiveness. When a pressure difference exists across the shaft seal (e.g., there is a differential pressure between the two sides of the shaft seal), the wear on the shaft seal will more quickly result in a leak. In the field of surface and sub-sea vehicle design, for example, leakage through the shaft seals is expected and typically addressed by either pumping the leaked fluid back out of the vehicle and/or pumping a lubricant through the shaft seal, thus displacing any water leakage. In many applications, the added complexity of such pump systems is not acceptable or desired due to weight, complexity, and cost; however, a leak mitigation system is nonetheless necessary to extend the service life of the vehicle.
Accordingly, a need exists for a shaft seal that mitigates leaks, such shaft seals being suitable for use in pressurized environments where zero or near-zero leakage is acceptable.